The invention relates to a lamp/reflector unit comprising
a reflector body provided with a concave reflecting surface having an optical axis,
a neck-shaped portion at the reflector body around the optical axis, this neck-shaped portion having a free end and being provided at its outer surface with a relief extending cross to the optical axis,
an electric lamp provided with contact pins, which lamp is mounted in the reflector body, while its contact pins project outwards at the free end of the neck-shaped portion. Such a unit is known from GB 2 153 986-A.
Lamp/reflector units, which were originally intended for colour slide projection and to be held in this case at the edge of the reflector body lying on its largest diameter, are now also used to obtain decorative illumination. The units are then mostly held at the contact pins. In order to permit mounting of a reflector unit in a holder in a more reliable manner than when using the clamping force of electrical connection terminals on the contact pins of a unit, the unit according to the aforementioned GB 2 153 986-A has a relief at the surface of the neck-shaped portion. Clamping members at a holder for the unit can cooperate with this relief and can ensure that the unit is fixed. In order that the reflector body with the neck-shaped portion can be formed in an inexpensive indivisible mould, according to the aforementioned Application a reflector body is manufactured having a neck-shaped portion without a relief, is manufactured and it is not until then that the relief is provided by grinding one or more grooves in the neck-shaped portion.
A disadvantage of this known unit is that a groove thus obtained leads especially with the use of glass as construction material to a mechanical weakening of the neck-shaped portion, as a result of which rupture can occur. Another disadvantage with the use of glass is that there is too much spread with respect to the dimensions of the neck-shaped portion to guarantee a good retention of the unit by a holder.